Help a new kid out

[killgore]

Alright guys, I'm 17 and a just graduated senior from a school who has a study area around engineering. My daily driver is a 1973 f250. So I do know some about mechanics and such. Okay so here is my design proposal

I want to build an electric go kart with some sort of regen braking involved. The reason I want to add the regen braking is because of the massive motor braking potential and no reason to burn up even more energy as heat by using brakes (I will have brakes involved). I was thinking about using two alternators mounted like a hub motor would be, one in each rear wheel. I would like the top speed to be around 20-25 with my 250 lbs 6'2 self in it. Any help to get me pointed in the right direction in terms of motor selection, drivetrain, etc. would be appreciated. Can I build my own controller for it? Thanks in advance

 

[Felineman]

Please fill out your profile and there is an electric vehicle section http://www.diygokarts.com/vb/forumdisplay.php?f=15 that could lead you in the right direction.

 

[itsid]

We don't know if you can build your own controller;
other than yourself, noone can
If it's possible?
Of course it is, building a motor controller isn't hard at all with just minor soldering skills;
designing it properly is what makes it a true challenge.

So can you design a motor controller?

regenerative breaking is nice.. but on karts it's very close to useless I'm afraid.
the weight, the duration of coasting and most of all the quality of the battery cells all work against you.
So the amount of energy you can restore is very little;

But it's a nice idea and it's still better than nothing so if can (design or afford the additional costs) than go for it.

two alternators as hubmotors?
okay.. well possible of course, but I wouldn't call that a good idea;
first: both motors must be 100% identical (make, model, batch, internal resistance, number and gauge of windings as well as make and type of the bearings!)
other than that and you might find one motor to be faster than the other one under the very same conditions. (1rpm difference is enough to have your kart dragging to the left or right)

and second:
with one controller you will run into bad steering behaviour in corners under laod
in slow corners both wheels have full grip and turn at the same rate (massive understeering)
in fast corners the inner wheel will have close to NO grip and can (loss of physical resistance) use up all the energy from the batteries, it'll spin free and use up all the energy so the outer wheel has not enough power anymore.. or worse: the inner wheels motor will burn out.

So careful with that

Two motors on a live axle is much more convenient,
since minor differences will be eliminated.
What's left is the difference in efficiency and load, but that doesn't affect the karts sefety

as for speed and such, see my sticky in this forum;
it'll give you an idea what power is needed under what circumstances.

'sid

 

[killgore]

Please fill out your profile and there is an electric vehicle section http://www.diygokarts.com/vb/forumdisplay.php?f=15 that could lead you in the right direction.

I was pretty sure this was located in the electrical section. Maybe I'm wrong?

 

[killgore]

We don't know if you can build your own controller;
other than yourself, noone can
If it's possible?
Of course it is, building a motor controller isn't hard at all with just minor soldering skills;
designing it properly is what makes it a true challenge.

So can you design a motor controller?

regenerative breaking is nice.. but on karts it's very close to useless I'm afraid.
the weight, the duration of coasting and most of all the quality of the battery cells all work against you.
So the amount of energy you can restore is very little;

But it's a nice idea and it's still better than nothing so if can (design or afford the additional costs) than go for it.

two alternators as hubmotors?
okay.. well possible of course, but I wouldn't call that a good idea;
first: both motors must be 100% identical (make, model, batch, internal resistance, number and gauge of windings as well as make and type of the bearings!)
other than that and you might find one motor to be faster than the other one under the very same conditions. (1rpm difference is enough to have your kart dragging to the left or right)

and second:
with one controller you will run into bad steering behaviour in corners under laod
in slow corners both wheels have full grip and turn at the same rate (massive understeering)
in fast corners the inner wheel will have close to NO grip and can (loss of physical resistance) use up all the energy from the batteries, it'll spin free and use up all the energy so the outer wheel has not enough power anymore.. or worse: the inner wheels motor will burn out.

So careful with that

Two motors on a live axle is much more convenient,
since minor differences will be eliminated.
What's left is the difference in efficiency and load, but that doesn't affect the karts sefety

as for speed and such, see my sticky in this forum;
it'll give you an idea what power is needed under what circumstances.

'sid

I wasn't looking at the regen braking really for the regenerative part of it, rather just the pull to reduce some load off of the brakes. So what you are saying is to join two motors by a common driveshaft? I have an idea of what I'm looking for in terms of alternators. Can I use alternators or is there a better motor? I was thinking of using two deep cycle batteries and if i can't use that, just two car batteries.

And I have the mechanical abilities to possibly make a controller, but is there something to point me towards how to "design" one?

 

[itsid]

I wasn't looking at the regen braking really for the regenerative part of it, rather just the pull to reduce some load off of the brakes.

Ah I see, but the motors will induce a current anyways if you don't add a clutch (you shouldn't) no matter if you collect the energy or not.
but true enough, if you do collect, the motors will break a little harder

The reason I want to add the regen braking is because of the massive motor braking potential and no reason to burn up even more energy as heat by using brakes...

the heat though will be bigger with regen braking than without
(more currents) just the brake pads will be slightly cooler perhaps.

So what you are saying is to join two motors by a common driveshaft?

the actual axle yes...
(because it's reducing the parts count and thus weight )

I have an idea of what I'm looking for in terms of alternators. Can I use alternators or is there a better motor?

Alternators can be used.
I think most need some modification to make them work properly, but basically they'll work.
The thing is: they're not made for the task, and by that they're not ideal for what you want to do. And as a result: of course there are better motors for what you wanna do.

I was thinking of using two deep cycle batteries and if i can't use that, just two car batteries.

The number of batteries is very related to the need of the motors and the amount of energy stored per cell vs the amount you want/need per hour of driving time.
a 48V motor will require at least four 12V batteries of course;
so think about the batteries the moment you have the motors and controller figured out.
Because in the end you might find yourself in the need of eight batteries and car batteries will be off the list because of their size.

And I have the mechanical abilities to possibly make a controller, but is there something to point me towards how to "design" one?

So you can solder but you don't know how to design the controller...
That is indeed the hardest part of the DIY controller.
You can search the nets for plans and advice, maybe find something that'll match the desired power and voltage, maybe you'll need to modify the plans to match.
I don't know what you want or need exactly so please ask google yourself.
Many open source or homemade controllers out there.
In this forum section there is for example one DIY controller incl the schematics available.
IIRC kibble made it a few years back.. (should be two threads)

But modifying such premade controller will be a matter of trial and error if you didn't have a good experience in designing electronics.

So maybe your best bet is to find a commercial controller that matches your needs.. maybe even the cheaper solution here.

'sid

 

[xXPhasemanXx]

Here's a diagram for a 12V motor controller. Perhaps this may help you on the basis of controllers? Idk, it might help you in the design stage.

 

[killgore]

Okay I was honestly looking for the "cheap" route. I figured since car alternators charge to 14.X volts that you could run the batteries in a parallel and the alternators would do just fine at 12 volts. I also thought since they were bigger than starters that they would be a better choice than the starter karts I have seen. Lastly alternators put up with a huge amount of heat (my alternator on my truck has been clicking away for quite a while ow at 250 degrees) that they would be decent for a bit longer than the short bursts of speed that the starter karts have

 

[landuse]

It was posted in the right section

 

[itsid]

Okay I was honestly looking for the "cheap" route. I figured since car alternators charge to 14.X volts that you could run the batteries in a parallel and the alternators would do just fine at 12 volts. I also thought since they were bigger than starters that they would be a better choice than the starter karts I have seen. Lastly alternators put up with a huge amount of heat (my alternator on my truck has been clicking away for quite a while ow at 250 degrees) that they would be decent for a bit longer than the short bursts of speed that the starter karts have

Yes, that's all true, but you do know that an alternator is not a DC motor, don't you?

it's providing a three phase alternating current.. and if you just apply a DC current to it nothing will happen!
(it'll jump to a position according to the used phase and shift and stay right there)

It's not as easy as attaching a DC controller

brushless rc controllers might work, but you'll need a rather expensive one I'm afraid.
And it depends on the Alternator if it works or not.
Most use field coils whereas RC motors use permanent magnets, so
you need to power the field coils as well (DC I think)

And to make your own controller you'll need to either measure back emf to find the rotation of the shaft and shift the currents to the next coil, or use a hall effect sensor to do so.
the latter need to be inside the alternator ..

It's doable (and has been done multiple times already)
but it's not an easy task.

'sid

PS the diagram is for a ~10W 12V on-off drill motor.. NOT EVEN CLOSE to what a DC electric vehicle motor controller would look like